Extended use of filter aid in oil

ABSTRACT

Methods for frying food including supplying cooking fluid to a fryer apparatus, frying food in the cooking fluid so that used cooking fluid including degradation products including surfactants are produced therein and food residue accumulates in the fryer apparatus, adding the treatment compound capable of selectively reducing the amount of the surfactants to the used cooking fluid, and permitting the treatment compound to remain within the fryer apparatus and settle upon the food residue while continuing the food frying process.

This is a continuation of application Ser. No. 07/794,794 filed on Nov.19, 1991, now U.S. Pat. No. 5,200,224, which is a continuation ofapplication Ser. No. 07/518,312, filed on May 7, 1990, abandoned, whichis a continuation of application Ser. No. 07/099,134, filed on Sep. 21,1987, abandoned.

FIELD OF THE INVENTION

The present invention relates to methods for frying foods. Moreparticularly, the present invention relates to methods for controllingthe quality of fats and oils during the food frying process. Still moreparticularly, the present invention relates to methods for controllingthe quality of cooking oils generally comprising triglycerides duringthe food frying process. Still more particularly, the present inventionrelates to such methods for controlling food frying processes conductedin a batch-type operation.

BACKGROUND OF THE INVENTION

A number of recognized processes exist for both the batch and continuousfrying of various foods using cooking or frying oils. In each of theseprocesses there is a recognized tendency for the oils which are used todecompose, forming various chemical products therefrom. These chemicalproducts include free fatty acids, along with other impurities andcontaminants, including food residue or "crumb" produced during thisprocess itself, along with the products formed by the breakdown of theoils used and the interaction of the oils with food products addedthereto. It is also known that in all of these processes the presence ofthese materials in the cooking oil, as well as the degradation of theoil itself, eventually results in degradation of the frying propertiesof the oil, until the oil is no longer useful.

A highly successful approach to the problems of the degradation ofcooking oils, and the consequent poor cooking products produced thereby,is set forth in U.S. Pat. No. 4,330,564 to Friedman. This patentdiscloses a fryer oil treatment utilizing expanded rhyolitic materialand water, in amounts of from about 33 to 75 wt. % of the composition,for such treatment processes. This material is preferably used incombination with a food-compatible acid, and the particular process towhich this patent is directed employs a system in which once treatmentis completed the residue of the composition of that invention is removedfrom the treated oil by means well known in the art for this purpose,i.e. filtering. The oil is thus preferably filtered hot, and with a handfilter or a filter machine, and the cooking process is then permitted tocontinue. This patent thus discloses that in typical operations usedcooking oil can be treated after each frying meal or at the end of eachfrying day. Filters useful in these inventions are also set forth inthis patent, and include as a preferred filter one described in U.S.Pat. No. 4,052,319.

This material has thus become highly significant in a commercial sensein connection with various batch-type processes which are generally usedin the retail food industry in areas where used fryer cooking oil ismixed with the composition, including the porous carrier material, andthe residue then filtered from the oil. The presence of the water inthese compositions results in dispersion of the porous carrier materialthroughout the hot oil.

The use of these food-compatible acids was previously disclosed inClewell, Jr. et al, U.S. Pat. No. 3,947,602, disclosing the use ofvarious absorbents, such as diatomaceous earth, activated carbon and thelike, to remove contaminants from the used cooking oil, again in aprocess where filtration is employed in connection with the used oil.

In co-pending U.S. patent application No. 035,071, filed on Apr. 6,1987, assigned to the assignee of the present application, a continuoustreatment process is disclosed in which the oil is continuouslyrecirculated through a cooking zone in the recirculation zone, and therecirculating oil is continuously treated with these treatmentcompounds, which are capable of selectively reducing the content ofsurfactants produced from the use of the cooking oil to substantiallyincrease the useful life of the oil in this process. Once again in theseprocesses, as shown in the drawings in this pending patent application,the treatment procedure includes a filtering medium, upon which thetreatment material is deposited as it contacts the used oil, and fromwhich it is then removed.

The search has therefore continued for methods for improving the foodfrying processes, particularly in batch-type operations.

SUMMARY OF THE INVENTION

In accordance with the present invention, these and other objects havenow been realized by the applicant's discovery of a method for fryingfood comprising providing a supply of cooking fluid or fryer cooking oilin a fryer apparatus, frying food in the supply of cooking fluid so thatused cooking fluid, including degradation products includingsurfactants, are produced therein and food residue accumulates in thefryer apparatus, adding a treatment compound capable of selectivelyreducing the amount of the surfactants in the used cooking oil, andpermitting the treatment compound to remain within the fryer apparatusand settle upon the food residue therein while continuing the foodfrying process.

In accordance with one embodiment of the method of the presentinvention, the method includes intermittently adding the treatmentcompound to the used cooking fluid while continuing the food fryingprocess. In a preferred embodiment, the method includes removing theused cooking fluid, the food residue and the treatment compound from thefrying apparatus at the termination of food frying process. In a morepreferred embodiment, the method also includes separating the usedcooking fluid from the food residue and the treatment compound, andreturning the used cooking fluid to the frying apparatus for continuingthe food frying process.

In accordance with another embodiment of the method of the presentinvention, the treatment compound is capable of selectively adsorbing orabsorbing surfactants thereonto, and preferably the treatment compoundcomprises a treatment powder.

In accordance with another embodiment of the method of the presentinvention, the treatment compound comprises a porous rhyolitic material,and preferably one including between about 33 and 75 wt. % water. In apreferred embodiment, the treatment compound includes a food compatibleacid, preferably citric acid.

In accordance with another embodiment of the present invention, themethod includes heating the cooking fluid within the fryer apparatus ata predetermined location within the fryer apparatus, whereby the foodresidue accumulates at a location in the fryer apparatus below thatpredetermined location.

BRIEF DESCRIPTION OF THE DRAWING

The following detailed description of the present invention can be morefully appreciated with reference to the Figure, in which:

FIG. 1 is a front, elevational, prospective drawing of a fryer apparatusused in accordance with the method of the present invention.

DETAILED DESCRIPTION

The treatment compound which is disclosed in U.S. Pat. No. 4,330,564 andwhich comprises water, food-compatible acid and porous rhyolite orperlite carrier, is disclosed for use in direct contact with used hotcooking oil. It is thus stated in this patent that this compositionremoves or neutralizes the effect of certain undesirable impurities fromthe used cooking oil, such as soluble food juices and fatty acids whichhave an adverse effect on the cooking oil, particularly with respect toits useful lifetime and cooking characteristics. This patent alsodiscloses that these compositions provide easy filtration once treatmenthas been completed, and that in fact there is no absolute need for thefilter cake or filter machine with the composition of the invention, butrather a simple hand filtration is all that is required. This patentstrictly discloses and claims, however, that upon filtration the treatedoil can then be used for further cooking.

In accordance with the present invention, however, it has now beendiscovered that these types of treatment compositions, which have nowbeen found (as disclosed in co-pending U.S. patent Ser. No. 035,071,filed on Apr. 6, 1987) to reduce the presence of akaline contaminantmaterials (ACM's) in these systems and, in particular, to reduce thesurfactant content of these cooking fluids or oils. This priorapplication thus included a recognition that there is continuousbuild-up of these ACM's in these systems, and that the use of thiscomposition to contact the used cooking oil for short periods of timecan reverse this process. The application of this principle tobatch-type systems is the subject of the present application. Moreparticularly, in accordance with this method it has now been found thatthe use of filtration can be severely limited, and in fact in many caseseliminated entirely, by adding the treatment compound itself directly tothe cooking apparatus in question and permitting it to remain therein,and that this can be done with a number of positive effects, and ratherunexpectedly with no significant negative effects. Thus, apart fromachieving its initial effect of reducing the presence of these ACM's,and in particular reducing the content of the surfactants generated inthe used oil so as to substantially increase the life of that oil, ithas also now been quite unexpectedly found that the continued presenceof the treatment compound in the cooking oil environment during furtherfrying in the oil not only does not produce any negative side effects,but creates additional positive factors in the overall cooking process.

More particularly, during the frying process various food residues,sediments and "crumb" products are produced in the oil, and these tendto settle out into the bottom of the fryer apparatus. The continuedpresence of this food residue in the apparatus, however, can have anegative impact on the overall frying process, and upon the life of theoil. The sediment or crumb material can continue to circulate throughoutthe oil bath, thus continuing to have a negative impact on the variousproperties of the oil, as well as depositing on food therein. Byemploying the present process, however, and by thus applying theabove-mentioned treatment compounds directly to the fryer bath, thisnegative impact is alleviated by the physical presence of the treatmentcompound on top of the food residue or crumb sediment at the bottom ofthe fryer apparatus. This in itself further contributes to the life ofthe oil during the cooking process.

Furthermore, by employing the present method and leaving the treatmentcompound within the oil bath during continued food processing or frying,the residual activity of the treatment compound itself is fullyutilized. Thus, the essential characteristic of this treatment compoundin terms of preventing build-up of deposits on the inside of fryer pots,and the consequent establishment of a cleaner and more efficient fryingprocess, the provision of oleophobic properties with food thus allowingthe production of fried food products therein without the oily residuepreviously found on such products, diminishing the effect of certaincolored materials from used cooking oils, the possible removal of toxicmaterials therefrom, and the overall increase of the life of the cookingoil used therein, is accomplished to a maximum degree by retention ofthe treatment compound within the oil during the extended food fryingprocess.

It has also unexpectedly been found that the presence of this treatmentcompound, which is preferably in the form of a treatment powder, doesnot have an adverse effect on the food product which is producedtherein. This is contrary to what one of ordinary skill in this artwould have expected. It would thus have been expected that the presenceof this powder material within the cooking oil would result in theundesirable deposition of a sandy powder or "grit" on the surface of thefood, but in fact this is found not to be the case. Not wishing to bebound by any particular theory of the mechanism with which this isavoided, it is believed that the treatment compound not only primarilyMettles to the bottom of the frying apparatus, but that in addition anyfloating or suspended particles of the treatment compound containedwithin the bath are propelled away from the frying food by water andother food juices which are purged from the food during heating withinthe frying oil. In addition, residual fines floating at the surface ofthe oil are moved by the effects of surface tension to the meniscus ofthe oil at the fryer's walls and adhere thereto out of the active fryingsystem.

This benefit of utilizing the method of the present invention is morefully realized if it is conducted intermittently throughout the entirefood frying process until that process is terminated on a batch basis.Thus, upon each additional supply of treatment compound to the usedcooking oil further advantage is taken of the settlement of thetreatment compound or powder upon the food residue or crumb material atthe bottom of the fryer apparatus, thus further preventing these foodresidues from rising in the oil due to agitation or convective forceswithin the oil.

The overall effect of this process is to thus reduce the need forfrequency of filtering, or in fact to eliminate filtering altogether, sothat one can simply discard the oil when it has been exhausted, and atthe same time realize all of the other beneficial effects of thesetreatment compounds as previously described.

Turning to the Figure, a typical batch fryer vat 1 is shown therein.Such a vat includes an upper useful cooking area 3, which is generallyrectangular in configuration which includes an upper opening 2, definedby rectangular rim 4. The cooking area extends downwardly to a lowerportion 5, at which level within the vat heating coils 8 are generallymaintained, which are not actually shown in the Figure, but arerepresented by the dotted lines in the Figure. The vat itself, however,continues downwardly from that level into a cold well area 7, which isgenerally connected by tapered wall portions 9 to the lower portion 5 ofthe vat 1, and which terminate in bottom or base 11 extendingtherealong. The entire vat 1 can then be filled with cooking fluid oroil, including both the cold well portion 7 and the main cooking portion3, and by activation of the heating coil 8 the oil can be brought tocooking temperature, so that food can enter through the upper opening 2and be placed into the cooking oil, generally being maintained in thatposition by a basket or screen which is mounted on the rim 4 while thefood is cooked within the oil bath.

A drain or spigot 13 generally extends from the cold well 7 near thebase 11, and the spigot 3 includes a valve 14, so that when desired theoil, along with food residue and other materials within the fryer vat,can be removed therefrom.

During the food processing itself food residue which breaks off from thefood within the basket mounted within the fryer vat 1 will generallyfall downwardly into the cold well 7 and be retained therein, whilepieces of the residue or crumb material can circulate within the bathduring further use. In accordance with the present method, however,after removal of the food basket, the treatment compound of the presentinvention can be added directly into the oil through the opening 2 tocontact the used and heated oil within the bath. It can thus accomplishits primary purpose of improving the quality of the oil and reducing theACM's and surfactants therein, and then settle downwardly to cover thefood residue or crumb material at the bottom of the cold well 7 alongthe bottom wall 11 thereof. This process can be repeated intermittentlythroughout the cooking process, that is as additional batches of foodare fried in the oil by being placed in the upper portion 3 thereof, bythe addition of further amounts of treatment compound afterpredetermined periods of use. In each such case the presence of thetreatment compound will further inhibit the recirculation of additionalfood residue which has gathered along the bottom wall 11 of the fryervat itself.

It is generally preferred that there be a cold well 7 below the heatercoils or other heating apparatus within the oil. It is preferred thatthere thus be some distance between the bottom wall 11 and the heatingcoils to permit the build-up of food residue, and in accordance with thepresent invention the application of treatment compound thereon. It isthus not desirable that this entire space be taken up by these solidmaterials so that they eventually come into direct contact with theheating coils. Thus in those systems without a cold well, or with asmall distance between the bottom wall 11 and the heating coil 8, itwould be desirable to drain the fryer vat more frequently. The reasonfor this is that contact with the solid material or overlying of thecrumb and/or treatment powder can result in burning out the heatersthemselves, or in any event promote the formation of pyrolysis productswithin the sediment, which can be harmful. After this predeterminedperiod of time, the vat 1 can thus be drained through the spigot 13 andvalve 14 (if available), so that the used oil along with the foodresidue or crumb material and the used treatment powder exits from thefryer vat. This material can be collected, and either by centrifugation,filtration or other means, the used oil can be separated from the solidstherein, which can then be discarded. The used oil can then be returnedto the fryer vat 1 for further service. In this manner, the longer lifeof the oil as accomplished by using the treatment compounds of thisinvention is fully taken advantage of without the need for constant orimmediate filtering, and again in many cases with a complete eliminationof the filtering process itself i.e., without filtering the cooking oil.The consequence of considerable savings in time and labor which resultfrom use of this method can be a significant advantage to the user.

As for the treatment compound itself, this is a material which iscapable of selectively but not necessarily exclusively reducing the ACMor surfactant content of the oil, and in most preferred form ispresently an active filter aid designated LIFE, which comprises anon-alkaline, non-dusting, non-irritating powder material which isdesigned to remove or control the surfactants formed during use ofdrying oils. It is believed that this powder material slows thedegradation of heated oils by slowing down the hydrolysis and rate ofoxidation of the oil along with the subsequent development of surfactantand/or precursors species therein.

The LIFE (or otherwise branded) powder material itself consists of anexpanded, rhyolitic, obsidian perlite material with an amorphoussilicate structure. Furthermore, the powder compositions employed hereincomprise the porous rhyolite carrier and water, and preferablysufficient water so that when contacted with hot fats and oils above theboiling point of water the water steams and disperses the compositionthroughout the oil. Thus, the composition preferably contains from about33 to about 75 wt. % water. In a preferred embodiment the compositioncomprises the porous carrier, water, and a food compatible acid, such ascitric acid, tartaric acid, acetic acid, phosphoric acid, malic acid andmixtures thereof, with the preferred food compatible acid being citricacid. The overall composition preferably contains between about 2 and 10wt. % of the food compatible acid, and more preferably between about 4and 6 wt. % thereof.

The rhyolitic materials themselves are rendered "expanded" or porous bymethods well known in the art, such as by heat expansion. Thus, theserhyolitic materials are initially heated to remove substantially all ofthe free moisture content, and the dried material is then directed to a"popper" where it is exposed to the flame of a gas jet at temperaturesgenerally in the range of about 1480° C. The rhyolite material is thenallowed to expand to produce the porous rhyolite carrier material usedin this invention, which generally has a low density and a sphericalshape. Preferably, the material has sizes in the ranges of from about 8to about 120 mesh, more preferably from about 20 to about 80 mesh, andmost preferably from about 40 to about 60 mesh. The porous spheres actas carriers both for the water and, when used, the food compatible acidsuch as the citric acid into the hot fryer oil. An average analysis ofthis inorganic material, which is of a variable composition due to itsnatural formation, includes a compositional analysis on a percentagebasis as follows:

    ______________________________________                                        Silica            75.62%                                                      Alumina          12.02                                                        Ferric oxide     2.36                                                         Calcium oxide    0.83                                                         Magnesium oxide  0.40                                                         Sodium oxide     1.56                                                         Potassium oxide  6.10                                                         Loss on Ignition 0.91                                                         ______________________________________                                    

There are a considerable number of other treatment powders which arebeing employed as filter aide in this industry. These includediatomaceous earth, which primarily comprises a silica powder material,and which is obtainable from various sources; a zeolitic and absorbentmineral base, FRYLIGHT, a product of Kaiser Aluminum Co.; a calcium andmagnesium hydroxide material fused with diatomaceous earth, which issold under the name MICROSWEET, a product of Manville Corporation; and amagnesium silicate material sold under the name MAGNESOL, a product ofReagent Chemical Research Inc. As has been discovered by applicants,however, from among these materials only the above-deScribed rhyoliticmaterial can successfully selectively reduce the ACM or surfactantcontent of the oil to substantively low amounts when used in accordancewith the method of the present invention, and thus achieve theunexpected superior results hereof.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

I claim:
 1. A method of frying food comprising providing a supply ofcooking oil for use in a food frying process in a fryer apparatus,frying said food in said supply of cooking oil whereby said cooking oilincluding degradation products comprising surfactants are producedtherein and food residue accumulates in said fryer apparatus, adding atreatment compound, directly in said cooking oil, said treatmentcompound reducing the amount of said surfactants to said used cookingoil, permitting said treatment compound to remain within said fryerapparatus and settle upon said food residue while continuing said foodfrying process, intermittently adding additional amounts of saidtreatment compound to said used cooking oil while further continuingsaid food frying process, and carrying out said method without filteringsaid cooking oil.
 2. The method of claim 1 wherein said treatmentcompound is capable of selectively absorbing said surfactants thereonto.3. The method of claim 14 wherein said treatment compound is capable ofselectively adsorbing said surfactants thereonto.
 4. The method of claim2 or 3 wherein said treatment compound is a treatment powder.
 5. Themethod of claim 4 wherein said treatment compound includes afood-compatible acid.
 6. The method of claim 5 wherein saidfood-compatible acid comprises citric acid.
 7. The method of claim 1wherein said treatment compound comprises a porous rhyolitic material.8. The method of claim 7 wherein said porous rhyolitic material includesbetween about 33 and 75 wt. % water.
 9. The method of claim 1 includingheating said cooking oil in said fryer apparatus at a predeterminedlocation within said fryer apparatus whereby said food residueaccumulates at a location in said fryer apparatus below saidpredetermined location.